Display Apparatus and Display Method

1. A display apparatus, comprising: a decoder that obtains high dynamic range (HDR) video data representing a luminance of each pixel by a code value; a control circuit; and a display device, wherein the control circuit: converts the HDR video data into HDR video using a first electro-optical transfer function (EOTF); determines, for each pixel of the HDR video data, whether the code value of the pixel is included in a first range of less than a first code value or a second range of greater than or equal to the first code value, to extract a first region including a pixel having a code value included in the first range and a second region including a pixel having a code value included in the second range, the first EOTF representing a conversion curve indicating a correspondence between a code value and a luminance, the conversion curve having a shape in which a slope of a tangent to the code value increases with an increase in the code value, the first code value being a code value corresponding to a first point at which a tangent having a predetermined slope is in contact with the conversion curve; and generates adjusted data in which a sharpness gain of the first region is set to be higher than a sharpness gain of the second region in the HDR video data, the first region and second region sharpness gains being used to correct a contour of the HDR video; and the display device applies the adjusted data to the HDR video and displays a resulting HDR video having the contour corrected, and wherein the control circuit selectively performs conversion using the first EOTF and conversion using a second EOTF depending on a maximum luminance of the HDR video data, the second EOTF having a curve different from the first EOTF in a range in which a code value is greater than a knee point code and being used to convert HDR video data having a code value corresponding to a luminance that is greater than a maximum display luminance into HDR video having the maximum display luminance as a maximum luminance, the maximum display luminance indicating a maximum luminance displayable by the display device, and in a case where the control circuit performs the conversion using the first EOTF: the control circuit further extracts, in the first region, a third region including a pixel having a code value included in a third range of less than the knee point code and a fourth region including a pixel having a code value included in a fourth range of greater than or equal to the knee point code; and the control circuit generates the adjusted data in which a sharpness gain of the third region is set to be higher than a reference value by a first value, and a sharpness gain of the fourth region is set to be higher than the reference value by a second value less than the first value, and the sharpness gain of the second region is set to be lower than the reference value by a third value, the reference value representing a value of a sharpness gain to be referred in the generating of the adjusted data.

2. The display apparatus according to claim 1 , wherein the second EOTF has, as the knee point code, a code value of a pixel corresponding to an ordinal position of a number of a predetermined proportion of all of a plurality of pixels of the HDR video data when the plurality of pixels are arranged in ascending order of code value.

3. The display apparatus according to claim 1 , wherein in a case where the control circuit performs the conversion using the second EOTF: the control circuit determines, for each pixel of the HDR video data, whether the code value of the pixel is included in a fifth range that is a code value range in which a slope of a tangent to the second EOTF is less than the predetermined slope or a sixth range that is a code value range in which the slope of the tangent to the second EOTF is greater than or equal to the predetermined slope, to extract a fifth region including a pixel having a code value included in the fifth range and a sixth region including a pixel having a code value included in the sixth range; and the control circuit generates the adjusted data in which a sharpness gain of the fifth region is set to be higher than the reference value by a fourth value and a sharpness gain of the sixth region is set to be lower than the reference value by a fifth value.

4. The display apparatus according to claim 3 , wherein the second EOTF has two change points with an increase in code value, the two change points being a second point at which the slope of the tangent changes from less than the predetermined slope to greater than or equal to the predetermined slope and a third point at which the slope of the tangent changes from greater than or equal to the predetermined slope to less than the predetermined slope, and the control circuit extracts, in the fifth region, a seventh region including a pixel having a code value included in a seventh range of less than a second code value corresponding to the second point and an eighth region including a pixel having a code value included in an eighth range of greater than or equal to a third code value corresponding to the third point, and extracts, as the sixth region, a region including a pixel included in the sixth range of greater than or equal to the second code value and less than the third code value.

5. The display apparatus according to claim 4 , wherein in the case where the control circuit performs the conversion using the second EOTF: the control circuit further extracts, in the seventh region, a ninth region including a pixel having a code value included in a ninth range of less than the knee point code, and a tenth region including a pixel having a code value included in a tenth range of greater than or equal to the knee point code; and the control circuit generates the adjusted data in which each of a sharpness gain of the ninth region and a sharpness gain of the tenth region is set to be higher than the reference value by the fourth value equal to the first value.

6. The display apparatus according to claim 5 , wherein the control circuit adjusts the sharpness gain of the fourth region in the case where the control circuit performs the conversion using the first EOTF, and adjusts a sharpness gain of the eighth region in the case where the control circuit performs the conversion using the second EOTF, and the control circuit adjusts the sharpness gain of the second region in the case where the control circuit performs the conversion using the first EOTF, and adjusts the sharpness gain of the sixth region in the case where the control circuit performs the conversion using the second EOTF.

7. A display method, comprising: obtaining high dynamic range (HDR) video data representing a luminance of each pixel by a code value; converting the HDR video data into HDR video using a first electro-optical transfer function (EOTF); determining, for each pixel of the HDR video data, whether the code value of the pixel is included in a first range of less than a first code value or a second range of greater than or equal to the first code value, to extract a first region including a pixel having a code value included in the first range and a second region including a pixel having a code value included in the second range, the first EOTF representing a conversion curve indicating a correspondence between a code value and a luminance, the conversion curve having a shape in which a slope of a tangent to the code value increases with an increase in the code value, the first code value being a code value corresponding to a first point at which a tangent having a predetermined slope is in contact with the conversion curve; generating adjusted data in which a sharpness gain of the first region is set to be higher than a sharpness gain of the second region in the HDR video data, the first region and second region sharpness gains being used to correct a contour of the HDR video; applying the adjusted data to the HDR video, and displaying a resulting HDR video having the contour corrected; selectively performing conversion using the first EOTF and conversion using a second EOTF depending on a maximum luminance of the HDR video data, the second EOTF having a curve different from the first EOTF in a range in which a code value is greater than a knee point code and being used to convert HDR video data having a code value corresponding to a luminance that is greater than a maximum display luminance into HDR video having the maximum display luminance as a maximum luminance, the maximum display luminance indicating a maximum luminance displayable by a display device; and in a case where conversion is performed using the first EOTF: further extracting, in the first region, a third region including a pixel having a code value included in a third range of less than the knee point code and a fourth region including a pixel having a code value included in a fourth range of greater than or equal to the knee point code; and generating the adjusted data in which a sharpness gain of the third region is set to be higher than a reference value by a first value, and a sharpness gain of the fourth region is set to be higher than the reference value by a second value less than the first value, and the sharpness gain of the second region is set to be lower than the reference value by a third value, the reference value representing a value of a sharpness gain to be referred in the generating of the adjusted data.

8. A display apparatus, comprising: a decoder that obtains high dynamic range (HDR) video data representing a luminance of each pixel by a code value; a control circuit; and a display device, wherein the control circuit: converts the HDR video data into HDR video using a first electro-optical transfer function (EOTF); determines, for each pixel of the HDR video data, whether the code value of the pixel is included in a first range of less than a first code value or a second range of greater than the first code value, to extract a first region including a pixel having a code value included in the first range and a second region including a pixel having a code value included in the second range, the first EOTF representing a conversion curve indicating a correspondence between a code value and a luminance, the conversion curve having a shape in which a slope of a tangent to the code value increases with an increase in the code value, the first code value being a code value corresponding to a first point at which a tangent having a predetermined slope is in contact with the conversion curve; and the display device displays the HDR video obtained as a result of conversion by the control circuit, using adjusted data obtained as a result of adjustment by the control circuit, and wherein the control circuit selectively performs conversion using the first EOTF and conversion using a second EOTF depending on a maximum luminance of the HDR video data, the second EOTF having a curve different from the first EOTF in a range in which a code value is greater than a knee point code and being used to convert HDR video data having a code value corresponding to a luminance that is greater than a maximum display luminance into HDR video having the maximum display luminance as a maximum luminance, the maximum display luminance indicating a maximum luminance displayable by the display device, and in a case where the control circuit performs the conversion using the first EOTF: the control circuit further extracts, in the first region, a third region including a pixel having a code value included in a third range of less than the knee point code and a fourth region including a pixel having a code value included in a fourth range of greater than or equal to the knee point code; and the control circuit generates the adjusted data in which a sharpness gain of the third region is set to be higher than a reference value by a first value, and a sharpness gain of the fourth region is set to be higher than the reference value by a second value less than the first value, and the sharpness gain of the second region is set to be lower than the reference value by a third value, the reference value representing a value of a sharpness gain to be referred in the generating of the adjusted data.

9. A display method, comprising: obtaining high dynamic range (HDR) video data representing a luminance of each pixel by a code value; converting the HDR video data into HDR video using a first electro-optical transfer function (EOTF); determining, for each pixel of the HDR video data, whether the code value of the pixel is included in a first range of less than a first code value or a second range of greater than the first code value, to extract a first region including a pixel having a code value included in the first range and a second region including a pixel having a code value included in the second range, the first EOTF representing a conversion curve indicating a correspondence between a code value and a luminance, the conversion curve having a shape in which a slope of a tangent to the code value increases with an increase in the code value, the first code value being a code value corresponding to a first point at which a tangent having a predetermined slope is in contact with the conversion curve; generating adjusted data in which a sharpness gain of the first region is set to be higher than a sharpness gain of the second region in the HDR video data, the first region and second region sharpness gains being used to correct a contour of the HDR video; applying the adjusted data to the HDR video, and displaying a resulting HDR video having the contour corrected; selectively performing conversion using the first EOTF and conversion using a second EOTF depending on a maximum luminance of the HDR video data, the second EOTF having a curve different from the first EOTF in a range in which a code value is greater than a knee point code and being used to convert HDR video data having a code value corresponding to a luminance that is greater than a maximum display luminance into HDR video having the maximum display luminance as a maximum luminance, the maximum display luminance indicating a maximum luminance displayable by a display device, and in a case where conversion is performed using the first EOTF: further extracting, in the first region, a third region including a pixel having a code value included in a third range of less than the knee point code and a fourth region including a pixel having a code value included in a fourth range of greater than or equal to the knee point code; and generating the adjusted data in which a sharpness gain of the third region is set to be higher than a reference value by a first value, and a sharpness gain of the fourth region is set to be higher than the reference value by a second value less than the first value, and the sharpness gain of the second region is set to be lower than the reference value by a third value, the reference value representing a value of a sharpness gain to be referred in the generating of the adjusted data.